“In the 4-billion-odd-year history of life on Earth, primary endosymbiosis is thought to have only happened twice that we know of, and each time was a massive breakthrough for evolution. The first occurred about 2.2 billion years ago, when an archaea swallowed a bacterium that became the mitochondria.
The second time happened about 1.6 billion years ago, when some of these more advanced cells absorbed cyanobacteria that could harvest energy from sunlight. These became organelles called chloroplasts.
And now, scientists have discovered that it’s happening again. A species of algae called Braarudosphaera bigelowii was found to have engulfed a cyanobacterium that lets them do something that algae, and plants in general, can’t normally do – “fixing” nitrogen straight from the air, and combining it with other elements to create more useful compounds.”
Endosymbiosis. That’s a good name for it. The article says this process has been going on for a 100 million years and is still probably a work in progress. These nitrogen fixing cyanobacteria haven’t reached the advanced state of dependence that mitochondria and chloroplasts now display.
Well, the biologists will be playing around with this experiment in progress for the next hundred years and I expect they’ll learn plenty. One day we’ll probably have chloroplasts of our own and spend a few hours in the sun every day to improve our green complexions.